The influence of sulfur contamination on the corrosion-fatigue behavior of a polycrystalline superalloy used in aero-engines is considered. Samples tested under a variety of environmental conditions (including exposures to air, SO x gas, and salt) are characterized through a suite of high-resolution characterization methods, including transmission electron microscopy (TEM), secondary ion mass spectroscopy (nanoSIMS), and atom probe tomography (APT). The primary effect of sulfur contamination is to accelerate the crack growth rate by altering the failure mechanism. The SIMS and TEM analyses indicate Cr-Ti sulfide particle formation at grain boundaries ahead of and around oxidized cracks. The APT analysis suggests that these particles then oxidize as the crack propagates and are enveloped in chromia. The chromia is surrounded by a continuous layer of alumina within the cracks. All of the sulfur detected was confined within the particles, with no elemental segregation found at grain boundaries.
Nickel disc corrosion is an important area within the gas turbine engine, with the potential to affect the lives of critical rotating parts. To understand the influence of corrosion on such components, it is essential to generate material data in a representative environment; hot corrosion in conjunction with cyclic loading. A comprehensive assessment of the behaviour of alloys U720Li and RR1000 in a laboratory-simulated environment has been undertaken to explore and replicate corrosion-fatigue features that have been identified in service. Key parameters such as salt loading (flux) and variations in mechanical stress cycle have been examined and have shown to modify the corrosion morphology and resulting fatigue life of the material. This paper is part of a thematic issue on the 9th International Charles Parsons Turbine and Generator Conference. All papers have been revised and extended before publication in Materials Science and Technology.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
The mechanical behaviour of three ultra-high strength steels has been assessed; AerMet100, 300M and the recently developed corrosion resistant high strength steel, MLX-17. Material heat treatment profiles have been utilised to provide performance optimised for the aerospace industry and specimens have been tested to explore tensile and fatigue properties, in particular when combined with pre-strain to simulate the effects of overload. Testing of this kind has not been reported within the literature, particularly amongst ultra-high strength and corrosion-resistant steels. Baseline mechanical performance for all three materials in their heat-treated conditions has been established and properties such as yield strength and ultimate tensile strength have been assessed following a 75% and 95% pre-strain as well as fatigue in combination with a 75% and 95% pre-strain. Under all loading conditions, resultant tensile mechanical properties are not seen to witness a substantial degradation in performance, but an improvement in terms of yield strength and UTS, due to the role of work hardening. An alloy comparison has been carried out and responses are seen to vary slightly as a result of material microstructure. Correlation of pre-strain and pre-fatigue results with respect to baseline properties and microstructure has contributed to advancing the understanding of the mechanical behaviour of the aforementioned ultra-high strength steels.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.